BEIJING (AP) — It was the scenario strategists from Beijing to Washington worried about: Kim Jong Il of North Korea dies suddenly, before the isolated regime can complete a transfer of power to his young son and rejoin disarmament talks with the U.S.

With news Monday of Kim’s death, the impoverished country known to be pursuing nuclear weapons plunged further into uncertainty, raising risks for the region.

Neighbors worry that political maneuvering in Pyongyang could spill over into missile launches or other aggression, though analysts give such acts a low probability. Tens of thousands of American troops are stationed in South Korea and Japan in this heavily armed, jittery corner of the world. China wants to keep its socialist neighbor stable — and avoid a flood of refugees — but also free from American and South Korean influence.

“If you asked experts what could happen to bring the regime down, it would be the sudden death of Kim Jong Il. That has happened now,” said Victor Cha, a former U.S. National Security Council director for Asian affairs under President George W. Bush and now a senior adviser at the Center for Strategic and International Studies, an American think tank. “We’re potentially at a watershed moment for the region.”

Its politics opaque in normal times, Pyongyang is likely to slow decision-making, upending efforts to restart nuclear disarmament talks just as the U.S. and North Korea seemed on the verge of resuming them. After months of delicate discussions, Washington was poised to announce a donation of food aid this week followed by an agreement with Pyongyang to suspend a uranium enrichment program, people close to the negotiations told The Associated Press.

U.S. Secretary of State Hillary Rodham Clinton said Monday the United States is still looking for better relations with the North Korean people despite the “evolving situation” there. “We both share a common interest in a peaceful and stable transition in North Korea as well as ensuring regional peace and stability,” she said in Washington.

Tentative reforms to build up its listless economy and better the lives of North Koreans — 3 million of whom or more than 10 percent of the population are underfed, the U.N. says — may also be put on hold.

Kim’s death caught North Korea’s power brokers at a fragile time, in the midst of grooming his youngest son, Kim Jong Un, who is in his late 20s, to succeed him. Though the elder Kim had a stroke in 2008, hastening plans to find a successor, his health had seemingly improved, allowing him to travel more frequently, resume a more public role and prepare for a longer power transition like the two-decade-long one he enjoyed under his father.

One test will be a long-planned celebration in April for the 100th anniversary of the birth of Kim’s father and revolutionary North Korean founder Kim Il Sung — an event meant to lend credibility to the bloodline succession. Feverish construction has been under way in Pyongyang, while overseas critics of the regime have accused it of holding back food so that it can lavish its people with heftier supplies for the anniversary.

North Korea watchers are focused on the now abbreviated succession, looking for signs of whether the Workers Party and military will rally around Kim Jong Un or whether challenges will arise.

Domestic unrest may percolate, analysts said, as North Koreans tire of poverty and the mobile phones and Internet connections that are a product of recent reforms leave them better informed about the outside world.

The two-day gap between Kim’s death Saturday on a train and its public announcement Monday underscored the government’s nervousness, analysts said.

“The fact that they delayed for two days goes to show that the North Koreans are worried about instability,” said Gong Keyu of Shanghai’s Institute for International Studies.

Also possible are armed incursions against South Korea or Japan in a bid to rally North Koreans around the leadership. North Korea’s shelling of a South Korean island last year was credited inside the North to Kim Jong Un, part of efforts to burnish his credentials as a fierce defender of the nation.

South Korea, North Korea’s opponent from the 1950-53 civil war and target of recurring provocations, put its armed forces on alert and President Lee Myung-bak conferred with President Barack Obama, who reaffirmed U.S. support. Japanese Prime Minister Yoshihiko Noda held an emergency national security council meeting with top Cabinet members to urge heightened vigilance.

China worries that a North Korean meltdown could send North Koreans pouring over its border, creating a potential security mess and straining the far from robust economy of its northeast.

“This is the single largest militarily armed zone in the world. It has been thus for decades and right now we’re at one of those critical junctures in post-1950 military history where we need to ensure that calm and restraint are exercised at an exceptionally difficult period of transition,” Australian Foreign Minister Kevin Rudd said.

Given the possible complications, cooperation among Washington, Seoul and Beijing is vitally needed to prevent problems in North Korea from destabilizing the region, the analysts said.

After Kim’s stroke in 2008, China rebuffed overtures by the U.S. and South Korea to discuss coordination if there were a regime collapse. Among the scenarios Washington wanted to explore: how to keep their militaries from clashing accidentally if both moved into North Korea and how to secure the uranium, plutonium and other materials in Pyongyang’s nuclear program.

Beijing’s influence over Pyongyang has grown in the past two years, its companies ramping up investment after North Korea exploded its second nuclear-test device and launched a long-range rocket, drawing U.N. sanctions.

Amid the uncertainty, analysts across the region also said Kim’s death provided North Korea an opportunity to break from its past of misplaced economic policies, diplomatic isolation and military threats by embracing outside help and full-throttle market-driven reforms.

The younger Kim studied in Switzerland and is closer in age to a younger group of reformers who have helped introduce programs to bring in foreign investment and allow limited use of mobile phones and the Internet, said Narushige Michishita, an expert at the National Graduate Institute for Policy Studies in Tokyo.

Those changes, however, are fueling expectations among North Koreans for change and are likely to make the road ahead rougher for the younger Kim, said Cui Yingjiu, a retired professor of Korean language at Peking University in Beijing and a former classmate of Kim Jong Il’s in Pyongyang in the 1960s.

“The old way of thinking is changing. The time for dictators has passed,” he said. “They see the changes in China. They’re only thinking about money now.”